The present invention relates to an exhaust manifold for an exhaust system of a combustion engine.
The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.
An exhaust manifold is a component of the exhaust system of combustion engines and has an internal pipe system and an outer shell which surrounds the internal pipe system. The exhaust manifold serves to unite or collect exhaust gas, which exits the individual cylinders and enters the exhaust manifold via inlet openings, and to feed the exhaust gas to a common exhaust-gas outlet. For this purpose, such an exhaust manifold is flange-mounted directly onto the engine or the cylinder head of the engine. Thus, the exhaust manifold, also called in the art as exhaust collector, forms the inlet zone of an exhaust system. As the combustion engine and thus the exhaust system, in particular the exhaust manifold, heats up and cools down, various zones of the exhaust manifold are exposed to different temperatures. As a result of the temperature differences, these zones of the exhaust manifold expand differently and thus are subject to different tensile and/or compressive forces. In addition, shear movements or plastic deformation may be experienced.
Regions adjacent to the inlet openings are exposed to less thermal stress than a region where the exhaust ducts of the internal pipe system come together in an outlet flange in which an increased mass flow of hot exhaust gases and a deflection of the exhaust gases takes place. This region forms an interface between outer system or outer shell and outlet flange, which is exposed to intense thermo-mechanical stress. Depending on the construction of the exhaust manifold and the connection to the outlet flange, it is necessary to adapt the outer system to the thermo-mechanical stress. This may be realized by making the wall thicker or by using material of higher quality. Also the addition of further components may increase the thermo-mechanical robustness at this critical region. The downside of all these approaches is the increase in weight and costs.
It would therefore be desirable and advantageous to provide an improved exhaust manifold to obviate prior art shortcomings.